1. Field of the Invention
The present invention relates to a corrosive resistant metal material covered with a conductive substance that is suitable for use in a component material requiring conductivity and corrosion resistance like electrical conductive material, electrical contact, electromagnetic wave shield, electrochemical electrode or antistatic material, more specifically, to a composite corrosive resistant metal material covered with a conductive substance that having both properties of each component substance, being usable for clad raw material for use in secondary working by its good surface lubricity and good releasability in processing, and being expected for application to a base material of various equipments.
2. Prior Art
In electrical equipments, many of them are used in environments exposed to atmosphere, fresh water or salty water. Contact material or conductive material used for power transmitting or signal transmitting in these equipments may be corroded in such environments, consequently, reliability of equipments may be impaired or life of equipments may be expired.
In an area of industry utilizing electrochemistry, metal is used abundantly for electrode of electroplating, molten salt electrolysis, desalination equipment or brine electrolysis, from the viewpoint of cost, stainless steel or nickel based alloy is used as electrode or insoluble electrode to prevent generation of lysate from electrode.
Metal exhibits excellent feature as a structural material, but iron based metal may not satisfy corrosion resistance. To solve this problem, metal material covered with polymer paint, polymer lining or polymer film may be used. However, according to environment or equipment to be used, covered polymer may be charged and may affect a bad influence such as damage to environment equipment by discharging.
Also in an electromagnetic wave shield, in order to give priority to electromagnetic shield characteristic, corrosion resistance of substrate metal may be sacrificed. In a fuel cell, metal is used for a separator or etc. of solid electrolyte type fuel cell, phosphoric type fuel cell, molten carbonate type fuel cell, solid polymer type fuel cell or methanol fuel cell. If a separator of a fuel cell is formed by metal, conductivity may be decreased by growth of passive state film of metal surface due to electrolysis phenomenon, in some cases corrosion may be caused.
To prevent these problems, covering layer having conductivity and corrosion resistant is generally formed over metal.
Conventionally, SUS (stainless steel), Ti (titanium) and Ti cladding material are known as corrosion resistant and conductive substrate, but these are not sufficient in conductivity. In case of SUS, contact resistance is increased by passive state film formed over surface, and in case of Ti, contact resistance is increased by large resistivity TiO2 (titanium oxide) formed over surface. As means for increasing conductivity, after secondary working, forming of conductive and corrosion resistant covering layer such as TiN (titanium nitride), TiC (titanium carbide) or Au (gold) is known, but there are problems that the processing causes high cost and is complicated.
Further, excellent corrosion resistant metal such as SUS or Ti is poor in lubricity at secondary working, therefore, there is problem that large deformation cannot be given by burning to mold at press working. To solve this problem, lubricant is used generally at press working, but man-hour is required for coating and removing of lubricant, moreover residual of lubricant has an adverse effect to performance.